This application is designed to provide Dr. Brynn Levy a program of mentored laboratory research to facilitate his development as an independent clinical scientist. During the course of his pre- and post- doctoral fellowships, Dr. Levy established comparative genomic hybridization (CGH), a DNA-based technique for identifying chromosome abnormalities, to be a valuable clinical diagnostic tool in routine clinical cytogenetics as well as in cancer cytogenetics. Current research is aimed at using this tool for detection of total aneuploidy in single cells. Since it is not feasible to culture and perform conventional cytogenetic analysis on single cells, CGH presents itself as an attractive technique for identifying chromosomal imbalances in single human cells. The application of this method would provide cytogenetic analysis of fetal cells derived from maternal circulation during pregnancy for prenatal diagnosis as well as of single cells obtained from 2-3 day old embryos for preimplantation diagnosis. The long term goals are therefore to (a) provide a non-invasive method of prenatal diagnosis and (b) increase the implantation rate of IVF and decrease the ensuing miscarriage rate by transferring only non-aneuploid embryos. To achieve these goals, the specific aims are: [1] Establish both a regular and DNA microarray CGH protocol which is highly sensitive, specific and reproducible for aneuploidy analysis of single human cells using single cells extracted from cell cultures by micromanipulation apparatus. [2] Determine the utility of the single cell CGH protocols for predicting diploidy and aneuploidy in fetal cells derived from the maternal circulation during pregnancy. [3] Assess the single cell CGH protocols for their ability to detect aneuploidy in embryos discarded because of a Fluorescence in situ hybridization (FISH) diagnosis of aneuploidy. [4] Assess the true frequency of mosaicism in: (A) embryos discarded because of a FISH diagnosis of aneuploidy and (B) embryos discarded because of a molecular diagnosis of an inherited disorder. Dr. Levy's development will be supported in his endeavors with protected research time, dedicated laboratory space, and Departmental and Institutional core facilities. He will be guided in the responsible conduct of research, and his development into an independent researcher will be enhanced by the serious involvement and commitment of his mentor and by the superb research and intellectual environment at Mount Sinai.